The present invention relates to a vane pump for supplying a working fluid to fluid pressure-operated equipment including hydraulically-operated equipment, which is represented by a torsional rigidity control unit for an automotive stabilizer (hereinafter referred to as an “active stabilizer”).
Usually, a vane pump of this type pressurizes a working fluid to a high pressure and delivers it by using a vane section consisting of a rotor that has a plurality of vanes that move in and out of the rotor with the rotation of the rotor, and a cam ring that houses the rotor. The vane pump has a flow control valve to prevent cavitation from occurring due to a negative pressure on the suction side at the time of high-speed rotation.
FIG. 5(a) is a sectional view showing one example of a vane pump that is the background art of the present invention, showing by being cut in the shaft center, and FIG. 5(b) is a sectional view taken along the line B-B of FIG. 5(a).
The vane pump 20 shown in FIG. 5 includes a flow control valve 11, a delivery passage 19, and a delivery port 12 for delivering the working fluid pressurized by the pump, a suction port 13 for drawing the working fluid from a tank (not shown) into the pump, and a reflux path 14 leading from the delivery port 12 to a suction passage 13b. 
In addition, the vane pump 20 includes a rotor 17a, a plurality of vanes 17b housed in the rotor 17 and moveable in and out with respect to the rotor 17a, a cam ring 17c that forms an inner peripheral surface with which the vanes 17b that project from the rotor 17a come into contact, a cover 18a and a side plate 18b that confine both sides of the rotor 17a etc., and a body 18 that houses these elements, which provide the pumping function, and by which the vane pump 20 functions as a vane pump.
The rotor 17a, the vanes 17b, and the cam ring 17c collectively form a vane section 17. The pumping function of the vane section 17 is the same as that of an ordinary vane pump, and so detailed explanation thereof is omitted.
A throttle valve 15 for throttling the flow path of the delivery port 12 is provided at the tip end of the flow control valve 11.
The flow control valve 11 carries out control so that a proper quantity of the working fluid, which is discharged to the delivery port 12 by the rotor 17 in constant rotation driven by torque from an automotive engine, is supplied at a proper pressure as required by hydraulically-operated equipment supplied with the working fluid.
At the same time, excess working fluid flows backward from the delivery port 12 to the suction port 13 through the reflux path 14 as indicated by a reflux Q in FIGS. 5(a) and 5(b). A shortage of suction to the vane section 17 at the time of high-speed rotation is compensated by this reflux Q, so that the occurrence of negative pressure is prevented, thereby avoiding cavitation.
The vane pump 20 with the flow control valve 11 performs the above-described function. However, some of the working fluid delivered from the vane section 17 forms the reflux Q, and the total quantity thereof is thus not supplied to the hydraulically-operated equipment. The vane pump 20 therefore has a poor efficiency, and is unsuitable for hydraulically-operated equipment that requires a large quantity of working fluid.
In order for the flow control valve 11 to perform the above-described function, the throttle valve 15 is essential. However, a torque loss occurs due to the throttle valve 15, and a solution to this problem has therefore been desired.
On the other hand, as a method for preventing cavitation, a method in which the returning working fluid is accelerated by a nozzle and returned into the tank has been proposed.
FIG. 6 is a sectional view of the essential portion of a different vane pump, another example of a vane pump that is background art to the present invention. This example is described in Patent Document 1.
This vane pump 30 includes a flow control valve 21, a suction port 23, a vane section 27, and a body 28, and has the same function as that of the vane pump 20 shown in FIG. 5. Furthermore, a tank 31 for storing the working fluid is provided adjacent to the vane pump 30.
The tank 31 includes a lead-out port 31b for sending the working fluid from the tank 31 to the suction port 23 of the pump 30, and a nozzle 31a for throttling and spraying the returning working fluid so that the working fluid is directed to the lead-out port 31b. 
In the above-described configuration, the vane pump 30 returns the working fluid into the tank 31 by accelerating the returning working fluid via the nozzle 31a to promote the suction of working fluid into the suction port 23, and thus prevents the occurrence of cavitation.
However, the flow control valve 21 still remains even in this vane pump 30. Therefore, a problem remains in that the above-described torque loss occurs, and the vane pump 30 is unsuitable for use in fluid pressure-operated equipment that should use most of the working fluid delivered from the vane section 27.
Moreover, the returning working fluid is supplied to the lead-out port 31b on the tank 31 side, which is farther from the suction port 23 of the pump 30, so that the acceleration effect is indirect in the pump 30. There may also be a problem in that air is entrapped in the working fluid in the tank 31 when the vehicle experiences vibration.
In addition, for the vane pump 30, the tank 31 must be disposed adjacent to it because of the layout of the lead-out port 31b considering the acceleration effect. Accordingly, the degree of freedom in designing the pump 30 is low.
Further, even if the suction is promoted with effort, the outflow direction is at a right angle considering the promotion of suction because the flow control valve 21 is arranged on the axis line of the suction port 23, which presents a problem of significantly decreased acceleration effect.
[Patent Document 1] Japanese Patent No. 3717850 (FIG. 4)
The present invention has been made to solve the above problems, and accordingly an object thereof is to provide a vane pump that can effectively utilize the total quantity of a working fluid delivered from a vane section, that can be used for fluid pressure-operated equipment that requires a high flow rate, that does not create a torque loss due to a throttle valve, and that can prevent the occurrence of cavitation caused by a shortage of suction.